ИСТИНА

Molecular oxygen plays a crucial role in plant metabolism. O2 is a source of reactive oxygen species (ROS) and oxidative stress. The excessively generated ROS play both signaling and protective function in mechanically stressed plants. Generation of ROS in microwounded cells is presumably mediated by the plasma membrane NADPH-oxidase that transfers electrons from cytoplasmic NADPH to extracellular oxygen with a concomitant production of ROS, H2O2 in particular. Microscopic injuries associated with ROS generation might be accompanied by oxygen concentration changes in the apoplast. Recent invention and elaboration of nanoscale electrochemical sensors provide the opportunity to test this hypothesis. Our data obtained by applying carbon-filled quartz micropipettes with platinum-coated tips (oxygen nanosensors) showed a considerable drop in oxygen concentration at Chara corallina cell surface in response to microperforation of the cell wall (CW). We tested possible involvement of the suppression of photosynthesis, the enhancement of respiration, and the activation of the plasmamembrane NADPH oxidase as an origin of oxygen decline upon CW microwounding. The results provide evidence for major role of plasmalemmal NADPH-oxidase in the discovered local drop of O2 content.